Figure 1.

Properties of spontaneous population activity in rat visual cortex. (A) Spontaneous state alternations of the ECoG between ECoG-synchronized and ECoG-desynchronized
states under urethane anesthesia. During synchronized states, the ECoG exhibits a
large-amplitude slow-wave pattern, whereas during desynchronized states the ECoG shows
a low-amplitude fast-wave pattern. (B) Bimodal distribution of ECoG amplitude RMS values under urethane anesthesia. Data
are from ~8 h of spontaneous ECoG recording. (C) ECoG power spectrograms of the two urethane states. Note the higher power in the
slow frequency range (< 3 Hz) in the synchronized state as compared to the desynchronized
state, whereas the reverse holds true for frequencies faster than 3 Hz. Also note
a distinct spectral peak at around 4 Hz in the desynchronized state. (D) Histogram showing the durations of each state (pooled data from three animals). While
on average, the length of each cycle is on the order of < 15 min, episodes of the
urethane synchronized state can last up to 50 min, especially during deep anesthesia.
(E) Averaged CSD plots along the depth of the cortex, triggered off of spontaneous activity
patterns (see Methods). Note that despite differences in amplitude, laminar CSD profiles
are qualitatively similar across states, with net densities of current flow being
highest in supragranular (SG) layers (Sync: AVRECSG/AVRECtotal = 0.684 ± 0.044; Desync: AVRECSG/AVRECtotal = 0.698 ± 0.022, ± SEM). Furthermore, no prominent granular (G) or infragranular
(IG) sink-source pairs are apparent in profiles of either state. These findings suggest
that spontaneous population activity is, to a large degree, governed by similar anatomical
network components in synchronized and desynchronized states.